The effect of replacement of R4Sn by germanium and silicon derivatives as the promoter for the catalyst system Re2O7/ SiO2-Al2O3 in the metathesis of hex-1-ene, and the system Re2O7/B2O3/SiO2-Al2O3 in the metathesis of methyl oleate, was studied. The new promoters react slowly with the rhenium oxide. An activation time of about 15 min at temperatures varying from 50 to 75 degreesC is required for obtaining a good catalytic activity. These promoters can replace the toxic tin compounds, although they give rise to lower turnover numbers in the metathesis of methyl oleate. (C) 2002 Elsevier Science B.V. All rights reserved.